Hello guzzio,
best regards to your kind neighbours 
Actually I’m not sure, but I think it might be a problem to find Strida Minis in Europe.
Please review yourself, at all pages below the Mini wasn’t mentioned;
http://strida.fr/boutique-velo-pliable
http://www.strida.de/
(Checked also the unofficial German dealer’s page without result.)
https://stridacanada.ca/product-category/strida-bikes/
not even Asian sites offer it (any longer?):
http://koreamtb.co.kr/shop/list.php?ca_id=1010&sort=&sortodr=&page=1
There’s one in India (?) - we can find here size info:
Deltacycles/Strida Mini
According to above it must be both, wheel and frame; as we know - thanks to Amuro - the Mini’s wheel size is definitely 14 inch.
Re: Gear ratios information about different models of Strida
And just one inch less doesn’t make the bike 12 cm shorter…
However, I believe you, respectively your neighbours, would have a hard time searching these rare bikes…
Isn’t there any chance to carry common 16" Stridas upright anywhere else in the motorhome?
You mentioned the width of the luggage box, ~ 1,10 m, could you tell also depth and height please?
Depending on the proportions of the trunk it might make sense to look for a different folding principle.
I could imagine that “package” designs will fit better, perhaps it’s also possible (by tilted or mirrored storing) to let two bikes “overlap” each other a bit - saving another few cm.
As a relatively small example I’ve picked out the Dahon Jifo:
http://dahon.com/bikes/jifo/
Alternative maybe Brompton?
http://www.brompton.com/
